What Do You Have? Is It COVID-19, Flu, a Cold or Allergies?

What Do You Have? Is It COVID-19, Flu, a Cold or Allergies?

By Dr. Mark Menolascino MD, MS

So you wake up tomorrow morning feeling like a truck ran over you and every muscle hurts, you have a runny nose, feel like you have a fever but you forgot to buy that thermometer last week at the store to know for sure, if you think about it too much you have a non-productive cough and you wonder if you have COVID-19 (short name for the novel or new CoronaVirus Infectious Disease that started in 2019).

Or is it the flu?  Or a cold? Or those allergies that spring up every year?  How can you tell???

This new virus, COVID-19 is in the coronavirus family of infectious disease, the same family of viruses as the common cold, and is named for the crown-like pattern of the outer proteins of the virus that attaches to human cells, especially in the lung but in almost every tissue of the body.  The virus hijacks the cell machinery to force it to make millions of new viruses then ruptures and kills the cell to release a new army of infectious warriors to continue the assault on your body.  That is why COVID-19 causes such a wide array of symptoms-pneumonia, blood clots, heart attacks, kidney/liver/skin damage, and neurological damage.  To help you figure what that battle inside you is doing and how worried to be about it, there are several go-to symptoms to differentiate COVID-19 from the flu, a cold, or allergies; but remember there are no absolutes and even the testing has false negatives and false positives.  If you have COVID-19 or the flu you need to make different decisions than if it is a cold or allergies.  The flu and COVID-19 can kill you, a cold or allergies can not.  Flu and COVID-19 are dangerous mainly due to secondary pneumonia, especially in older people and those with underlying illness-but I have seen it kill people of all ages and healthy or not.  The virus sneaks in and weakens the lungs or overwhelms the immune system/inflammation response and the chemicals released ‘drown’ the lungs.  The other concern is that a bacterial pneumonia can sneak in on the heels of a viral lung infection and cause a ‘double pneumonia’ this is very dangerous.

One of the tools I use to tell the difference between dangerous COVID-19 and flu versus a nuisance cold or allergies is this chart I made (feel free to share!):


Symptoms Chart

Last fall this was easy as COVID-19 did not exist!  Now the first questions to always ask in our new COVID-19 landscape is:

Have you lost the sense of smell or taste?

The sudden loss of taste or smell is unique to COVID-19 and can be the first (and luckily for some the only) symptom of COVID-19; I have never seen this with flu/colds/allergies.

The second big question is:

Are there body aches?

This is a symptom of both the flu and the COVID-19 but much more common with the flu. Most COVID-19 does not give you the ‘I can’t get out of bed’ body aches that the flu causes and allergies or a cold never do.

The third and most important question is (and has been since I was a medical student):

Are you having trouble breathing or shorter of breath with usual activities?

This is the red flag to seek medical advice.  You can ride out a fever, body aches, headaches, runny nose but if you trouble breathing, this can become an emergency very quickly.

The flu usually doesn’t cause shortness of breath right away unless that dreaded double pneumonia develops.  With COVID-19 is so dangerous because you can have shortness of breath/difficulty breathing rapidly and early in the illness BEFORE you get a full pneumonia; while with the flu, the pneumonia CAUSES the shortness of breath and is more predictable and slower.  Even ER doctors have trouble sorting this out, but I will help you by walking you through how I think of it when someone calls me, or I do a house call.  In medicine, I was trained as a specialist and my first motto is to do no harm; second is work as hard as you can to be right on with diagnosis and treatment but don’t make a mistake; third is to plan for the worst hope for the best.  If something bad is going on you want to be prepared, be ahead of a bad viral infection of any kind, and not miss an opportunity to fix the problem early or prevent a late complication.

So here are some ‘pearls’ from my medicine cabinet to yours:

  • COVID-19, the flu, a cold and allergies have different symptoms though there is much overlap, and can be hard to discern one versus the other, even for experienced doctors like me.
  • The main symptoms to watch and seek medical attention for is shortness of breath.
  • COVID-19 tends not to have the severe body aches that the flu causes, and this may be helpful to sort the two out and colds/allergies don’t do this.
  • Digestive symptoms, especially sudden and intense diarrhea, can be early and the only symptoms with COVID-19, usually later in flu illness and rarely with colds and never with allergies.
  • The sudden loss of smell or taste only happens with COVID-19.  Allergies can cause a loss of smell after weeks of congestion, but this does not happen suddenly and rarely happens with the flu or a cold-I have never seen it in 25 years of clinical medicine due to the flu.
  • Allergies have more chronic symptoms and vary with the season and do not come on suddenly like a viral illness onset like flu, COVID-19, or a cold.
  • Remember, the common cold is a coronavirus like COVID-19 but is a much less dangerous type of coronavirus.
  • COVID-19, the flu, and colds are contagious and good handwashing with soap is the key-wash your hands while you say the alphabet as this is the ideal duration to wash and you have done a thorough job.  Soap is the key as it surrounds the virus to wash away and protects you and others.
  • The flu has symptoms like the COVID-19, such as fever and body aches, but influenza usually doesn’t cause shortness of breath unless there is a secondary pneumonia, which will come up to a week after the start of symptoms.  With COVID-19 the first symptom may be shortness of breath.

With COVID-19, shortness of breath often occurs 5 to 10 days after the first sign of fever and sneezing is RARELY a symptom of COVID-19.  But remember, you can have allergies or a cold AND COVID-19!

COVID-19 symptoms usually appear 2 to 14 days after exposure.

The main symptoms of COVID-19 are:

  • Fever or chills
  • Cough
  • Shortness of breath or difficulty breathing
  • Fatigue
  • Muscle or body aches
  • Headache
  • Sore throat
  • New loss of taste or smell-very rare with the flu, colds, allergies
  • Congestion or runny nose
  • Diarrhea, Nausea or vomiting-much more likely to be COVID-19


We have made it into October, just in time for the ‘second wave’ of COVID-19 and the possibility of a double whammy with the flu and COVID-19.  For both, good handwashing is paramount and Vitamin D, as an immune modulator, seems to be a good choice.  Zinc at 30 mg has always been thought to be supporting immune function.  Vit C, especially powder mixed in water gargled and swallowed keeps the oral mucosa defenses up as well as overall immune support. A good probiotic to balance the gut microbiome keeps the immune system stronger and the correct blend of immune support nutrients can be the key to keep your defense strong.  As always, drinking enough water (1/2 ounce water per pound of body weight and remember more water if a fever as you ‘burn’ off extra water, avoiding processed food and eating whole foods, adding in the veggies and fruits to get at least 8 ‘colors’ a day for antioxidants and nutrients, and avoid alcohol and sugar which reduces your immune defense.  Be Smart, Be Kind, Stay Safe is our clinical and my life motto now.